Passage of exogenous thyroxine and of iodide between mother and foetus in pregnant rabbits

Serum proteins, including thyroxine‐binding proteins, in maternal and foetal rabbits

“…It has been shown (Hall & Myant, 1956) that when radioactive thyroxine is injected into pregnant rabbits very little radioactivity reaches the foetus if the injection is made early in pregnancy. If, however, the injection is made towards the end of pregnancy, at 24 hr after the injection the concentration of radioactive thyroxine in the foetal serum is found to have risen to nearly half the concentration in the maternal serum (Myant, 1958).…”

The Origin of Plasma Proteins in the Guinea Pig Fetus12

“…The very low activity in the fetal alpha globulins may reflect poor transfer, but it may merely indicate that this fraction is altered more extensively during iodination. It may be pertinent to this problem that I'," thyroxine which is bound to, and in effect labels, the alpha globulins without artificial iodination of the protein, is transferred in the rabbit from mother to fetus with about the same efficiency as albumin in the present study (10).…”

Whole Body Counter in Routine Tests of Hyperthyroidism Using Iodine 131

“…Hence the loss of thyroidal 1311 from the body is relatively slow even in hyperthyroid subjects; the shortest half life found was 18 days. STERLING & CHODOS (1956), found the turnover rate of thyroxine to be 16.9 yo per day in hyperthyroidism, but most of the liberated iodine will be reabsorbed in the thyroid, while the thyroxine excreted via the bile into the faeces is small (MYANT & POCHIN 1950, MYANT 1956). I n some patients, a 4-hour total body measurement was also made, but calibration was difficult because of the extrathyroidal iodide concentrating mechanisms of the salivary gastro-enteric cycle and the kidneys, all of which play an important role in the distribution of1311 at this time after administration (1963) suggested the extrapolation of the retention to zero time as an index of thyroid activity; however, unless the retention curve is extended for a prolonged length of time there will be a tendency to overestimate the thyroid uptake in euthyroid subjects.…”

“…Iodine may be concentrated in the mammalian ovary, particularly during the phase of follicular development (BROWN-GRANT 1961). A large fraction of radioiodine can be excreted in the milk of the lactating mother (MILLER & WEETCH 1955, HALL & MYANT 1956, POTTER et coll. 1959, GROSVENOR 1960.…”